Project: Discrete Preamp
My discrete preamp, which was based on the information in this Zetex datasheet.
There is also a PCB layout for this available which can be downloaded below.
It would be quite trivial to construct this on veroboard (as I did with my prototypes) but the PCB layout provided makes for a neater job.
This little preamp has excellent performance and very low noise. I have compared this to several commercial designs including Cambridge C500, Rotel RC971, Adcom GFP345 and it compared very favourably.
See the gallery images below for the schematic.
Note: there are a couple of mods - one in particular "C7" needs to be soldered to the bottom of the board.
RL (22k) is just a test load for simulation and is not required.
R7 (collector of Q2) has also been omitted and a link must be fitted in it's place.
Q3 (output transistor) dissipates around 260mW (collector current is ~18mA) - I fitted a TO92 heat sink to mine to keep it cool, although a heat sink is probably not really necessary.